The parasitic protist Trichomonas vaginalis transports glucose across the plasma membrane by facilitated diffusion. The Km of the transporter for glucose was 1.6 mM. The uptake of labelled glucose in a minimal medium not allowing growth reached saturation only after 2.5 h, indicating the turnover of storage carbohydrate. Organisms grown on glucose showed higher activities both of the transporter and of the subsequent metabolic pathway than organisms grown on maltose. At low external glucose concentrations the transport step was rate limiting, at higher levels a subsequent enzymatic step. The uptake mechanism for glucose of T. vaginalis resembled that of parasitic kinetoplastid protists and Entamoeba histolytica.